Seamless Switching Control Strategy from Grid-Connected to Islanded Mode for Shunt-Type Dynamic Voltage Regulator Under Nonlinear Loads

With the escalating number of sensitive electrical apparatus within the grid, the adverse effects of voltage sags have become increasingly apparent, driving the rapid development of research on shunt-type dynamic voltage regulator (S-DVR). Given that S-DVR has two independent operating modes, namely grid-connected and islanded mode, the significance of effective switching control strategies becomes particularly pronounced. However, considering that the current research on switching control strategies is mostly based on linear loads, this paper proposes a seamless cut-in control strategy from grid-connected to islanded mode applicable to nonlinear loads. The proposed control strategy ensures seamless switching at the control strategy level while achieving rapid turn-off of triodes for alternating current (TRIACs), reaching the purpose of seamless switching from grid-connected to islanded mode with satisfactory control effect. The effectiveness of the proposed seamless cut-in control strategy is confirmed by simulation results.